The present invention relates to belt-type power transfer assemblies and has particular reference to such power transfer assemblies having belt tensioning devices and to the use of such power transfer assemblies on rotary type combine harvesters.
In known combine harvesters, crop material is threshed and separated in a threshing and separating mechanism and the separated grain, together with impurities is fed to a cleaning mechanism for cleaning. In conventional combine harvesters final grain separation is accomplished by straw walkers. In rotary combine harvesters the crop material is subjected to a much more aggressive and positive separating action during a relatively prolonged period of time, whereby the efficiency of a rotary combine harvester usually is greater than that of a conventional machine.
In one type of rotary combine harvester a conventional transversely extending threshing mechanism having a threshing cylinder and a cooperable concave is combined with a rotary separating mechanism having a rotor of a width greater than that of the threshing mechanism and disposed parallel thereto with its ends extending transversely past the respective ends of the threshing mechanism. The rotary separating mechanism operates spirally to convey the crop material received from the threshing mechanism towards each of its ends, while submitting the crop to a separating action.
It has been experienced that in rotary combine harvesters of the type described, irregular feeding of crop material to the separating mechanism may cause plugging which eventually may result in a so-called "kill-stop" of said mechanism. Provided the drive train to the separating mechanism does not comprise other safety devices, such a "kill-stop" often would result in a major breakdown, such as the drive belt and/or pulleys breaking and/or shafts bending.
spring-loaded tensioning devices for belt-type power transfer assemblies maintain belt tension to provide a positive drive under a wide range of load conditions, including the aforesaid "kill-stop" conditions; however, such tensioning devices improve the operative life of the belt. On the other hand, fixedly positioned belt tensioning devices will not provide a positive drive under "kill-stop" conditions, but do significantly shorten belt life.